Perturbation of cell-cell and cell-substratum adhesion by secreted and cell-surface proteases plays an important role in dissemination of epithelial tumors. Multiple recent DNA microarray studies identified cell-surface serine protease hepsin as a transcript that is drastically overexpressed in metastatic prostate carcinomas. We hypothesize that overexpression of hepsin causes disruption of cell-cell and cell-substratum adhesion in prostate epithelial cells and, therefore, contributes to prostate cancer progression. To analyze the functional significance of hepsin overexpression in the context of a prostate gland in vivo, we have generated and are now analyzing transgenic mice expressing hepsin in prostate epithelia. Since development of prostate carcinoma may require multiple genetic modifications, we will investigate potential cooperation between hepsin and other oncogenes. To determine potential role for hepsin at different time points of prostate cancer progression, we will breed our hepsin transgenic mice with mouse models of prostate cancer that develop precancerous prostate lesions, or nonmetastatic prostate cancer. We reason that if hepsin is positively involved in prostate cancer progression, overexpression of hepsin in the precancerous prostate lesions will lead to the development of prostate carcinoma. If hepsin is involved in cancer dissemination, overexpression of hepsin in the nonmetastatic prostate tumors will lead to a transition from nonmetastatic to metastatic cancer. To determine the molecular mechanisms responsible for hepsin function, we will analyze the primary prostate epithelial cell lines overexpressing this protein. Overall, the studies in this project will help to determine the functional significance and molecular consequences of hepsin overexpression in prostate cancer.